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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package acme
import (
// ACME server response statuses used to describe Authorization and Challenge states.
const (
StatusUnknown = "unknown"
StatusPending = "pending"
StatusProcessing = "processing"
StatusValid = "valid"
StatusInvalid = "invalid"
StatusRevoked = "revoked"
// CRLReasonCode identifies the reason for a certificate revocation.
type CRLReasonCode int
// CRL reason codes as defined in RFC 5280.
const (
CRLReasonUnspecified CRLReasonCode = 0
CRLReasonKeyCompromise CRLReasonCode = 1
CRLReasonCACompromise CRLReasonCode = 2
CRLReasonAffiliationChanged CRLReasonCode = 3
CRLReasonSuperseded CRLReasonCode = 4
CRLReasonCessationOfOperation CRLReasonCode = 5
CRLReasonCertificateHold CRLReasonCode = 6
CRLReasonRemoveFromCRL CRLReasonCode = 8
CRLReasonPrivilegeWithdrawn CRLReasonCode = 9
CRLReasonAACompromise CRLReasonCode = 10
// ErrUnsupportedKey is returned when an unsupported key type is encountered.
var ErrUnsupportedKey = errors.New("acme: unknown key type; only RSA and ECDSA are supported")
// Error is an ACME error, defined in Problem Details for HTTP APIs doc
type Error struct {
// StatusCode is The HTTP status code generated by the origin server.
StatusCode int
// ProblemType is a URI reference that identifies the problem type,
// typically in a "urn:acme:error:xxx" form.
ProblemType string
// Detail is a human-readable explanation specific to this occurrence of the problem.
Detail string
// Header is the original server error response headers.
// It may be nil.
Header http.Header
func (e *Error) Error() string {
return fmt.Sprintf("%d %s: %s", e.StatusCode, e.ProblemType, e.Detail)
// AuthorizationError indicates that an authorization for an identifier
// did not succeed.
// It contains all errors from Challenge items of the failed Authorization.
type AuthorizationError struct {
// URI uniquely identifies the failed Authorization.
URI string
// Identifier is an AuthzID.Value of the failed Authorization.
Identifier string
// Errors is a collection of non-nil error values of Challenge items
// of the failed Authorization.
Errors []error
func (a *AuthorizationError) Error() string {
e := make([]string, len(a.Errors))
for i, err := range a.Errors {
e[i] = err.Error()
return fmt.Sprintf("acme: authorization error for %s: %s", a.Identifier, strings.Join(e, "; "))
// RateLimit reports whether err represents a rate limit error and
// any Retry-After duration returned by the server.
// See the following for more details on rate limiting:
func RateLimit(err error) (time.Duration, bool) {
e, ok := err.(*Error)
if !ok {
return 0, false
// Some CA implementations may return incorrect values.
// Use case-insensitive comparison.
if !strings.HasSuffix(strings.ToLower(e.ProblemType), ":ratelimited") {
return 0, false
if e.Header == nil {
return 0, true
return retryAfter(e.Header.Get("Retry-After")), true
// Account is a user account. It is associated with a private key.
type Account struct {
// URI is the account unique ID, which is also a URL used to retrieve
// account data from the CA.
URI string
// Contact is a slice of contact info used during registration.
Contact []string
// The terms user has agreed to.
// A value not matching CurrentTerms indicates that the user hasn't agreed
// to the actual Terms of Service of the CA.
AgreedTerms string
// Actual terms of a CA.
CurrentTerms string
// Authz is the authorization URL used to initiate a new authz flow.
Authz string
// Authorizations is a URI from which a list of authorizations
// granted to this account can be fetched via a GET request.
Authorizations string
// Certificates is a URI from which a list of certificates
// issued for this account can be fetched via a GET request.
Certificates string
// Directory is ACME server discovery data.
type Directory struct {
// RegURL is an account endpoint URL, allowing for creating new
// and modifying existing accounts.
RegURL string
// AuthzURL is used to initiate Identifier Authorization flow.
AuthzURL string
// CertURL is a new certificate issuance endpoint URL.
CertURL string
// RevokeURL is used to initiate a certificate revocation flow.
RevokeURL string
// Term is a URI identifying the current terms of service.
Terms string
// Website is an HTTP or HTTPS URL locating a website
// providing more information about the ACME server.
Website string
// CAA consists of lowercase hostname elements, which the ACME server
// recognises as referring to itself for the purposes of CAA record validation
// as defined in RFC6844.
CAA []string
// Challenge encodes a returned CA challenge.
// Its Error field may be non-nil if the challenge is part of an Authorization
// with StatusInvalid.
type Challenge struct {
// Type is the challenge type, e.g. "http-01", "tls-sni-02", "dns-01".
Type string
// URI is where a challenge response can be posted to.
URI string
// Token is a random value that uniquely identifies the challenge.
Token string
// Status identifies the status of this challenge.
Status string
// Error indicates the reason for an authorization failure
// when this challenge was used.
// The type of a non-nil value is *Error.
Error error
// Authorization encodes an authorization response.
type Authorization struct {
// URI uniquely identifies a authorization.
URI string
// Status identifies the status of an authorization.
Status string
// Identifier is what the account is authorized to represent.
Identifier AuthzID
// Challenges that the client needs to fulfill in order to prove possession
// of the identifier (for pending authorizations).
// For final authorizations, the challenges that were used.
Challenges []*Challenge
// A collection of sets of challenges, each of which would be sufficient
// to prove possession of the identifier.
// Clients must complete a set of challenges that covers at least one set.
// Challenges are identified by their indices in the challenges array.
// If this field is empty, the client needs to complete all challenges.
Combinations [][]int
// AuthzID is an identifier that an account is authorized to represent.
type AuthzID struct {
Type string // The type of identifier, e.g. "dns".
Value string // The identifier itself, e.g. "".
// wireAuthz is ACME JSON representation of Authorization objects.
type wireAuthz struct {
Status string
Challenges []wireChallenge
Combinations [][]int
Identifier struct {
Type string
Value string
func (z *wireAuthz) authorization(uri string) *Authorization {
a := &Authorization{
URI: uri,
Status: z.Status,
Identifier: AuthzID{Type: z.Identifier.Type, Value: z.Identifier.Value},
Combinations: z.Combinations, // shallow copy
Challenges: make([]*Challenge, len(z.Challenges)),
for i, v := range z.Challenges {
a.Challenges[i] = v.challenge()
return a
func (z *wireAuthz) error(uri string) *AuthorizationError {
err := &AuthorizationError{
URI: uri,
Identifier: z.Identifier.Value,
for _, raw := range z.Challenges {
if raw.Error != nil {
err.Errors = append(err.Errors, raw.Error.error(nil))
return err
// wireChallenge is ACME JSON challenge representation.
type wireChallenge struct {
URI string `json:"uri"`
Type string
Token string
Status string
Error *wireError
func (c *wireChallenge) challenge() *Challenge {
v := &Challenge{
Type: c.Type,
Token: c.Token,
Status: c.Status,
if v.Status == "" {
v.Status = StatusPending
if c.Error != nil {
v.Error = c.Error.error(nil)
return v
// wireError is a subset of fields of the Problem Details object
// as described in
type wireError struct {
Status int
Type string
Detail string
func (e *wireError) error(h http.Header) *Error {
return &Error{
StatusCode: e.Status,
ProblemType: e.Type,
Detail: e.Detail,
Header: h,
// CertOption is an optional argument type for the TLS ChallengeCert methods for
// customizing a temporary certificate for TLS-based challenges.
type CertOption interface {
// WithKey creates an option holding a private/public key pair.
// The private part signs a certificate, and the public part represents the signee.
func WithKey(key crypto.Signer) CertOption {
return &certOptKey{key}
type certOptKey struct {
key crypto.Signer
func (*certOptKey) privateCertOpt() {}
// WithTemplate creates an option for specifying a certificate template.
// See x509.CreateCertificate for template usage details.
// In TLS ChallengeCert methods, the template is also used as parent,
// resulting in a self-signed certificate.
// The DNSNames field of t is always overwritten for tls-sni challenge certs.
func WithTemplate(t *x509.Certificate) CertOption {
return (*certOptTemplate)(t)
type certOptTemplate x509.Certificate
func (*certOptTemplate) privateCertOpt() {}